Zeolytic sulfur guard

ABSTRACT

A composition useful for the adsorptive removal of hydrogen sulfide from a gas or liquid stream, the composition comprising ferric oxide and a zeolyte group. The zeolyte group may comprise aluminum and silicon at a ratio in the range from about 1 part aluminum to 100 parts silicon to about 100 parts aluminum to 1 part silicon, and have a mix of amorphous aluminosilicate and structured zeolyte, wherein the structured zeolyte comprises a distribution of zeolytic cells ranging in size from about 3 Angstroms to about 16 Angstroms. Also disclosed is a process for removing hydrogen sulfide from various process stream by contact with such a composition.

BACKGROUND OF DISCLOSURE

1. Field of the Disclosure

Embodiments disclosed herein relate generally to the removal of hydrogensulfide from hydrogen, carbon dioxide, natural gas, and hydrocarbonvapor or liquid streams. More specifically, embodiments disclosed hereinrelate to the use of an iron-based zeolytic material to adsorb hydrogensulfide.

2. Background

Hydrogen sulfide is a highly toxic and corrosive environmental pollutantwith an obnoxious smell that needs to be removed from various streamsfor pollution control, corrosion protection, as well as processrequirements in various industries. Natural gas processing complexes,refineries, sulfur processing chemicals industries, pharmaceuticalindustries, sugar industries, sewage treatment plants, carbon dioxidepurification systems, and bio-gas generating units are some of the majorindustries requiring removal of hydrogen sulfide from various processstreams.

A number of processes have been known and are in commercial use forremoving hydrogen sulfide from gas streams, including the Claus processand the Liquid Redox process. The Claus process is used for removinghydrogen sulfide from gases containing typically high concentration ofH₂S (more than 20% by volume H₂S). The Liquid Redox process is used forremoving hydrogen sulfide from gases containing typically lowconcentration of H₂S.

Processes using iron sponges (iron oxide deposited on wood shavings) ascatalyst have also been in use for removing hydrogen sulfide from gases.The major disadvantage with iron sponges and similar materials is thatthey cannot be regenerated, are used as only once-through catalysts, andmust be disposed as waste after use. Therefore, the cost of suchtreatment is high due to the use of stoichiometric quantities ofchemicals and also disposal of the used materials. Further, the extentto which the wood shavings can be loaded (loading capacity) with ironoxide is low, thus limiting the hydrogen sulfide removal capacity.

In other processes for hydrogen sulfide removal, zinc oxide or a mixtureof zinc oxide and copper oxide are used. Cost and the need for highertemperatures for effective removal are disadvantages for use of zinc andcopper, as the gas needs to be preheated prior to treatment.

SULFATREAT, a mixed metal oxide adsorbent, available from SULFATREAT,St. Louis, Mo., and SULFUR GUARD, available from MicroPure FiltrationInc., Mound, Minn., are two systems currently being used for removal ofhydrogen sulfide from various process streams. Removal of hydrogensulfide from various gas streams is also disclosed in U.S. Pat. Nos.7,556,671, 7,569,199, 7,481,985, 7,396,522, 6,040,259, and 4,831,206,among others.

The processes and catalysts used for the removal of hydrogen sulfidefrom various process streams have one or more disadvantages includingonce-through usage, high raw material costs, high disposal costs, andtemperature limitations. In some cases, the compositions used becomepyrophoric when contacted with hydrogen sulfide.

Accordingly, there exists a continuing need for alternative compositionsthat are useful for the removal of hydrogen sulfide from various processstreams.

SUMMARY OF THE DISCLOSURE

In one aspect, embodiments disclosed herein relate to a compositionuseful for the adsorptive removal of hydrogen sulfide from a gas orliquid stream, the composition comprising ferric oxide and a zeolytegroup, the zeolyte group: comprising aluminum and silicon at a ratio inthe range from about 1 part aluminum to 100 parts silicon to about 100parts aluminum to 1 part silicon; and having a mix of amorphousaluminosilicate and structured zeolyte; wherein the structured zeolytecomprises a distribution of zeolytic cells ranging in size from about 3Angstroms to about 16 Angstroms. In some embodiments, the zeolyte groupmay include clinoptilolite.

In another aspect, embodiments disclosed herein relate to a process forthe adsorptive removal of hydrogen sulfide from a gas or liquid stream,the process comprising: contacting a gas, liquid, or gas/liquid mixturehaving a first concentration of hydrogen sulfide with a compositioncomprising ferric oxide and a zeolyte group to produce an effluenthaving a second concentration of hydrogen sulfide less than the firstconcentration of hydrogen sulfide. The zeolyte group may comprisealuminum and silicon at a ratio in the range from about 1 part aluminumto 100 parts silicon to about 100 parts aluminum to 1 part silicon; andhave a mix of amorphous aluminosilicate and structured zeolyte; whereinthe structured zeolyte comprises a distribution of zeolytic cellsranging in size from about 3 Angstroms to about 16 Angstroms. In someembodiments, the zeolyte group may include clinoptilolite.

Other aspects and advantages will be apparent from the followingdescription and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified process flow diagram of a process for removinghydrogen sulfide from a process stream according to embodimentsdisclosed herein.

FIG. 2 is a simplified process flow diagram of a process for removinghydrogen sulfide and other impurities from a process stream according toembodiments disclosed herein.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to the removal ofhydrogen sulfide from hydrogen, carbon dioxide, natural gas, andhydrocarbon vapor or liquid streams. More specifically, embodimentsdisclosed herein relate to the use of an iron-based zeolytic compositionfor the adsorptive removal of hydrogen sulfide from various processstreams.

Embodiments disclosed herein may be used to reduce or remove hydrogensulfide from gas, liquid, or mixed vapor/liquid streams containinghydrogen sulfide. Natural gas process or production streams, refinerypetroleum streams, such as a cracker or reformer effluent or a partiallyor fully hydrotreated (including hydrodesulfurized) petroleum streams,hydrogen gas streams, such as a hydrogen gas effluent from a hydrogensulfide stripper or an amine absorption unit, carbon dioxide gasstreams, and numerous other streams may contain hydrogen sulfide. Priorto downstream processing or sale of a product stream, including pipelinesales streams, the hydrogen sulfide in these streams must be reduced orremoved, such as to protect against corrosion, poisoning of catalysts,and/or to meet various governmental or industry imposed standards.

In some embodiments, the concentration of hydrogen sulfide in streams tobe treated according to embodiments disclosed herein may be as high as10000 ppm or greater. In other embodiments, the concentration ofhydrogen sulfide in streams to be treated according to embodimentsdisclosed herein may be in the range from about 1 ppm to about 1000 ppm;in the range from about 5 ppm to about 500 ppm in other embodiments; andin the range from about 10 ppm to about 100 ppm in yet otherembodiments.

The hydrogen sulfide may be removed from process streams by contactingthe gas, liquid, or gas/liquid mixture containing hydrogen sulfide witha composition comprising ferric oxide and a zeolyte group. The zeolytegroup may include aluminum and silicon at a weight ratio in the rangefrom about 1 part aluminum to 100 parts silicon to about 100 partsaluminum to 1 part silicon, and may have a mix of amorphousaluminosilicate and structured zeolyte having a distribution of zeolyticcells ranging in size from about 3 Angstroms to about 16 Angstroms.Ferric oxide as used herein refers to iron (III) oxide (Fe₂O₃).Compositions comprising ferrous ferric oxide (Fe₃O₄), or mixtures offerric oxide and ferrous ferric oxide, and the above-described zeolytegroup may be used in other embodiments.

In some embodiments, the zeolyte group may comprise, include, contain,consist essentially of, or consist of clinoptilolite. Thus, the hydrogensulfide may be removed from process streams by contacting the gas,liquid, or gas/liquid mixture containing hydrogen sulfide with acomposition comprising ferric oxide and clinoptilolite according toembodiments disclosed herein. Ferric oxide as used herein refers to iron(III) oxide (Fe₂O₃). Compositions comprising ferrous ferric oxide(Fe₃O₄), or mixtures of ferric oxide and ferrous ferric oxide, andclinoptilolite may be used in other embodiments.

Contact of a gas, liquid, or gas/liquid mixture having a firstconcentration of hydrogen sulfide with a composition comprising ferricoxide and a zeolyte group, such as clinoptilolite, according toembodiments disclosed herein may produce an effluent having a secondconcentration of hydrogen sulfide less than the first concentration ofhydrogen sulfide. Contact of a process stream with a compositioncomprising ferric oxide and a zeolyte group, such as clinoptilolite,according to embodiments disclosed herein may reduce the concentrationof hydrogen sulfide in the process stream by at least 90 weight percentin some embodiments; by at least 95 weight percent in other embodiments;by at least 98 weight percent in other embodiments; by at least 99weight percent in other embodiments; by at least 99.5 weight percent inother embodiments; and by at least 99.9 weight percent in yet otherembodiments.

For example, a process stream having a concentration of hydrogen sulfidein the range from about 5 ppm to about 500 ppm may be contacted with acomposition comprising ferric oxide and a zeolyte group, such asclinoptilolite, according to embodiments disclosed herein, resulting inan effluent having a concentration of hydrogen sulfide in the range fromabout 0 ppm to about 10 ppm, where the effluent concentration is lessthan the inlet concentration. In some embodiments, hydrogen sulfide maybe removed to a concentration below detectable limits.

Compositions comprising ferric oxide and clinoptilolite according toembodiments disclosed herein may be contacted with the process streamsas a fixed bed (or static bed), a fluidized bed, a moving bed, or othermanners of contacting gases and liquids with a solid. In someembodiments, compositions comprising ferric oxide and a zeolyte groupsuch as clinoptilolite may be disposed as a fixed bed layer or layers ina vessel. In other embodiments, compositions comprising ferric oxide anda zeolyte group such as clinoptilolite may be disposed as a fixed bedlayer or layers in a vessel, where the vessel contains one or moreadditional layers containing structures or compositions for removingother impurities from the process stream, such as metals, water orhydroxide-containing compounds, nitrogen-containing compounds, andchlorine-containing compounds.

Compositions comprising ferric oxide and a zeolyte group such asclinoptilolite may be provided in any number of shapes and sizes assuitable for the type of service (fixed bed, fluidized bed, etc.). Forexample, the ferric oxide and clinoptilolite may be co-mingled, such ason a microscopic scale, at a ratio of ferric oxide to clinoptilolite inthe range from about 0.1 to about 10 parts of ferric oxide per part ofclinoptilolite. The resulting mixture may then be formed (e.g.,tabletted or extruded in the presence or absence of a binder) into aparticle. The mixing may be achieved using a blender, such as a ribbonblender or other powder mixing devices. In some embodiments, the blendedmaterials are mixed with water, acid or base, and a binder, such assilica, clay, titania, zirconia, alumina and the like to form anextrudable mixture. This mixture can be extruded and/or formed into anysuitable shape including cylinders, cubes, stars, tri-lobes,quadra-lobes, pellets, pills, spheres, or shapes containing hollow coresof varying diameters by suitable mechanical means. For example, theferric oxide, clinoptilolite and other components may be blended using aribbon blender and extruded using a KAHL pelletizer to produce pelletshaving a desired size. In other embodiments, blends of ferric oxide andclinoptilolite may be spray dried, or the structures containing anintimate blend of ferric oxide and clinoptilolite may be ground orotherwise comminuted, to form dusts, particles, powders, granules orother similar structures comprising ferric oxide and clinoptilolite. Insome embodiments, the compositions comprising clinoptilolite and ferricoxide may be in the form of cylinders having a diameter in the rangefrom about 2 mm to about 8 mm.

The structures and compositions comprising ferric oxide andclinoptilolite according to embodiments disclosed herein may contain abinder, such as alumina, silica, and other binders known to those ofskill in the art. In other embodiments, structures and compositionscomprising ferric oxide and clinoptilolite according to embodimentsdisclosed herein may contain at least one of sodium oxide zeolite,magnesium aluminosilicate, potassium aluminosilicate, calciumaluminosilicate, opaline silica, and Portland cement. Such structuresmay have a surface area of at least 3 m²/g, such as in the range fromabout 100 m²/g to about 400 m²/g in some embodiments. The structures andcompositions comprising ferric oxide and clinoptilolite according toembodiments disclosed herein may have a pore volume in the range fromabout 0.2 cc/g to about 0.65 cc/g.

Compositions comprising ferric oxide and a zeolyte group such asclinoptilolite according to embodiments disclosed herein preferentiallydo not contain zinc and copper. However, these metals may be present asimpurities in the ferric oxide or other raw materials used duringpreparation of the compositions. Thus, compositions comprising ferricoxide and a zeolyte group such as clinoptilolite according toembodiments disclosed herein may contain from 0 wt. % to less than 1 wt.% copper and from 0 wt. % to less than 1 wt. % zinc.

In some embodiments, compositions comprising ferric oxide andclinoptilolite according to embodiments disclosed herein may contain:0.1 to 90 weight percent sodium oxide zeolite; 0.1 to 90 weight percentmagnesium aluminosilicate; 0.1 to 90 weight percent potassiumaluminosilicate; 0.1 to 90 weight percent calcium aluminosilicate; 5 to50 weight percent Portland cement; 1 to 30 weight percent opalinesilica; 1 to 90 weight percent clinoptilolite; 1 to 90 weight percentferric oxide; 0 to less than 1 weight percent zinc; and 0 to less than 1weight percent copper.

In other embodiments, compositions comprising ferric oxide andclinoptilolite according to embodiments disclosed herein may contain: 5to 90 weight percent sodium oxide zeolite; 5 to 90 weight percentmagnesium aluminosilicate; 5 to 90 weight percent potassiumaluminosilicate; 5 to 90 weight percent calcium aluminosilicate; 10 to30 weight percent Portland cement; 5 to 20 weight percent opalinesilica; 5 to 80 weight percent clinoptilolite; 5 to 90 weight percentferric oxide; 0 to less than 1 weight percent zinc; and 0 to less than 1weight percent copper.

In addition to adsorption of hydrogen sulfide, compositions according toembodiments disclosed herein may also be useful for the adsorptiveremoval of various other sulfur containing species, including carbonylsulfide, carbon disulfide, and mercaptans, among others.

Contact of the hydrogen sulfide-containing process streams withcompositions comprising ferric oxide and a zeolyte group such asclinoptilolite according to embodiments disclosed herein may beperformed at temperatures, pressures, and flow rates commonly used forthe associated upstream and downstream processing steps. For example, aneffluent from a reformer may be fed to a fixed bed for removal ofhydrogen sulfide and/or other contaminants, where the effluent may befed directly to the fixed bed without any intermediate processes toincrease or decrease the temperature or pressure of the effluent. Inother embodiments, the temperature and/or pressure of the streams may beadjusted prior to contact, such as the compression of a hydrogen ornatural gas stream. In some embodiments, contact may be performed attemperatures in the range from ambient or about 10° C. to about 300° C.,pressures in the range from about 0.1 bar to about 50 bar, such as inthe range from about 3 bar to about 30 bar, and space velocities in therange from about 1 h⁻¹ to about 200 h⁻¹, such as in the range from about80 h⁻¹ to about 150 h⁻¹.

Contact of the hydrogen sulfide-containing process streams withcompositions comprising ferric oxide and a zeolyte group such asclinoptilolite according to embodiments disclosed herein may reacthydrogen sulfide with the ferric oxide to form non-stoichiometric ironsulfide (Fe_(x)S_(x), such as Fe₂S₃ or Fe₃S₄, for example). In someembodiments, the resulting composition including non-stoichiometric ironsulfide is not pyrophoric.

Referring now to FIG. 1, a process for removing hydrogen sulfide from aprocess stream according to embodiments disclosed herein is illustrated.A stream 10 containing hydrogen sulfide, such as a hydrogen recyclestream from a hydrogen sulfide stripper or a natural gas process stream,is fed to a vessel 12 for removing at least a portion of the hydrogensulfide from the stream. Vessel 12 may contain one or more beds 14containing compositions comprising ferric oxide and clinoptiloliteaccording to embodiments disclosed herein. The hydrogen sulfide in thefeed stream reacts with the composition, forming non-stoichiometricferric sulfide. An effluent 16 is recovered from vessel 12 having areduced concentration of hydrogen sulfide as compared to stream 10.

Referring now to FIG. 2, a process for removing hydrogen sulfide andother impurities from a process stream according to embodimentsdisclosed herein is illustrated. A stream 20 containing multipleimpurities, such as a reformer outlet stream containing hydrogenchloride, organic chlorides, olefins, and hydrogen sulfide, is fed to avessel 22 for removing at least a portion of the hydrogen chloride andhydrogen sulfide. Vessel 22 may contain one or more beds 24 containingcompositions for adsorbing at least a portion of the hydrogen chlorideand one or more beds 26 containing compositions comprising ferric oxideand clinoptilolite according to embodiments disclosed herein foradsorbing at least a portion of the hydrogen sulfide. One or more beds28 may also be provided to remove additional impurities, where theplacement of bed 28 may be above, intermediate, or below beds 24, 26. Aneffluent 30 is then recovered from vessel 22 having a reducedconcentration of both hydrogen sulfide and hydrogen chloride as comparedto stream 20.

As described above, embodiments disclosed herein provide processes andcompositions useful for the reduction or removal of hydrogen sulfidefrom various process streams. Specifically, compositions useful for thereduction or removal of hydrogen sulfide include ferric oxide and azeolyte group such as clinoptilolite. Ferric oxide and clinoptilolitemay be obtained from any of a number of sources. In some embodiments,the ferric oxide may be recovered from the pickling liquor of a steelmill, such as by roasting the pickling liquor containing ferric chlorideto produce ferric oxide powder (e.g., a beta phase ferric oxide sourcedfrom ferric chloride roasted at a high temperature). The clinoptilolite,a natural ore, may be obtained from various sources worldwide, and insome embodiments may be obtained from the Bear River Zeolite Company,Preston, Id.

Advantageously, embodiments disclosed herein may provide for theefficient reduction or removal of hydrogen sulfide from process streamsusing compositions including ferric oxide and a zeolyte group such asclinoptilolite. Such compositions may be formed using inexpensive rawmaterials, providing a cost savings over various prior art materialsused for a similar service. Additionally, following reaction of hydrogensulfide with compositions including ferric oxide and clinoptiloliteaccording to embodiments disclosed herein may produce anon-stoichiometric iron sulfide that is not pyrophoric, thus reducingthe costs for removal of spent adsorbents from a vessel as well as costsassociated with disposal or recycling of the spent material.

While the disclosure includes a limited number of embodiments, thoseskilled in the art, having benefit of this disclosure, will appreciatethat other embodiments may be devised which do not depart from the scopeof the present disclosure. Accordingly, the scope should be limited onlyby the attached claims.

1. A composition useful for the adsorptive removal of hydrogen sulfide from a gas or liquid stream, the composition comprising ferric oxide and a zeolyte group, the zeolyte group: comprising aluminum and silicon at a ratio in the range from about 1 part aluminum to 100 parts silicon to about 100 parts aluminum to 1 part silicon; and having a mix of amorphous aluminosilicate and structured zeolyte; wherein the structured zeolyte comprises a distribution of zeolytic cells ranging in size from about 3 Angstroms to about 16 Angstroms.
 2. The composition of claim 1, wherein the zeolyte group comprises clinoptilolite.
 3. The composition as claimed in claim 1, further comprising a binder.
 4. The composition of claim 1, further comprising at least one of sodium oxide zeolite, magnesium aluminosilicate, potassium aluminosilicate, calcium aluminosilicate, opaline silica, and Portland cement.
 5. The composition of claim 1, wherein the composition has a surface area of at least 10 m/g.
 6. The composition of claim 1, wherein the composition has a surface area in the range from about 100 m 2/g to about 400 m 2/g.
 7. The composition of claim 1, wherein the composition has a pore volume in the range from about 0.2 cc/g to about 0.65 cc/g.
 8. The composition of claim 1, wherein the composition is shaped in the form of a cylinder, cube, star, tri-lobe, quadra-lobe, pellet, pill, tablet, sphere, a shape containing a hollow core, or combinations thereof.
 9. The composition of claim 1, wherein the composition comprises from 0 wt. % to less than 1 wt. % copper and from 0 wt. % to less than 1 wt. % zinc.
 10. The composition of claim 1, wherein the composition comprises from about 0.1 to about 10 parts of ferric oxide per part of clinoptilolite.
 11. The composition of claim 1, wherein the composition comprises: 0.1 to 90 weight percent sodium oxide zeolite; 0.1 to 90 weight percent magnesium aluminosilicate; 0.1 to 90 weight percent potassium aluminosilicate; 0.1 to 90 weight percent calcium aluminosilicate; 5 to 50 weight percent Portland cement; 1 to 30 weight percent opaline silica; 1 to 90 weight percent clinoptilolite; 1 to 90 weight percent ferric oxide; 0 to less than 1 weight percent zinc; and 0 to less than 1 weight percent copper.
 12. A process for the adsorptive removal of hydrogen sulfide from a gas or liquid stream, the process comprising: contacting a gas, liquid, or gas/liquid mixture having a first concentration of hydrogen sulfide with a composition comprising ferric oxide and a zeolyte group, the zeolyte group: comprising aluminum and silicon at a ratio in the range from about 1 part aluminum to 100 parts silicon to about 100 parts aluminum to 1 part silicon; and having a mix of amorphous aluminosilicate and structured zeolyte; wherein the structured zeolyte comprises a distribution of zeolytic cells ranging in size from about 3 Angstroms to about 16 Angstroms; to produce an effluent having a second concentration of hydrogen sulfide less than the first concentration of hydrogen sulfide.
 13. The process as claimed in claim 12, wherein the zeolyte group comprises clinoptilolite.
 14. The process as claimed in claim 12: wherein the first concentration is in the range from about 5 ppm to about 500 ppm hydrogen sulfide; and wherein the second concentration is in the range from about 0 ppm to about 10 ppm hydrogen sulfide.
 15. The process of claim 12, wherein the gas, liquid, or gas/liquid mixture having a first concentration of hydrogen sulfide comprises at least one of: a natural gas process or production stream; a refinery petroleum fraction; a hydrogen gas effluent from a hydrogen sulfide stripper or an amine absorber; and a carbon dioxide gas stream.
 16. The process of claim 12, wherein the composition further comprising a binder.
 17. The process of claim 12, wherein the composition further comprises at least one of sodium oxide zeolite, magnesium aluminosilicate, potassium aluminosilicate, calcium aluminosilicate, and opaline silica.
 18. The process of claim 12, wherein the composition has a surface area of at least 10 m/g.
 19. The process of claim 12, wherein the composition has a surface area in the range from about 100 m 2/g to about 400 m 2/g.
 20. The process of claim 12, wherein the composition has a pore volume in the range from about 0.2 cc/g to about 0.65 cc/g.
 21. The process of claim 12, wherein the composition is shaped in the form of a cylinder, cube, star, tri-lobe, quadra-lobe, pellet, pill, tablet, sphere, a shape containing a hollow core, or combinations thereof.
 22. The process of claim 12, wherein the composition comprises from 0 wt. % to less than 1 wt. % copper and from 0 wt. % to less than 1 wt. % zinc.
 23. The process of claim 12, wherein the composition comprises from about 0.1 to about 10 parts of ferric oxide per part of clinoptilolite.
 24. The process of claim 12, wherein the composition comprises: 0.1 to 90 weight percent sodium oxide zeolite; 0.1 to 90 weight percent magnesium aluminosilicate; 0.1 to 90 weight percent potassium aluminosilicate; 0.1 to 90 weight percent calcium aluminosilicate; 5 to 50 weight percent Portland cement; 1 to 30 weight percent opaline silica; 1 to 90 weight percent clinoptilolite; 1 to 90 weight percent ferric oxide; 0 to less than 1 weight percent zinc; and 0 to less than 1 weight percent copper. 